1. Field of the Invention
The present invention relates to a golf club head.
2. Description of the Related Art
Regarding a material used for a golf club head, various proposals have been made. Japanese Patent Application Laid-Open No. 2002-35180 discloses a golf club head using a porous metal. As described in Paragraph [0021] of Japanese Patent Application Laid-Open No. 2002-35180, a position of a center of gravity can be optionally set by making at least a part of a face and/or at least a part of a crown of a porous metal, and appropriately setting a void ratio thereof.
Japanese Patent Application Laid-Open No. 11-151330 discloses a club head for golf having a head hitting part having a porous structure in order to enhance a hitting feel and a hitting sound. In the invention, a surface density on a face surface side of the head hitting part is precise, and an internal density on a back surface side thereof is coarse.
Japanese Patent Application Laid-Open No. 2003-135633 discloses a golf club head in which at least any one of a head body and a face member is made of a porous metal having porosity of 5 to 50%. A manufacturing method for subjecting a raw material metal having porosity of 10 to 90% to plastic forming to produce a porous metal having porosity of 5 to 50% is described in claim 8 of the document. In FIG. 7, a constitution in which metal plates are joined to both sides of a porous face member is disclosed.
A view showing the relationship between porosity and an elastic modulus of a porous metal made of a titanium alloy is described in The Japan Institute of Metal (Nihon-Kinzoku gakkai), Annual autumn meeting (the 135th) outline (2004), p. 466.